Massari S, Colonna R, Folena E
C.N.R. Unit for the Study of Physiology of Mitochondria, University of Padua, Italy.
Biochim Biophys Acta. 1988 May 9;940(1):149-57. doi: 10.1016/0005-2736(88)90019-3.
The surface density of the fluorescent probe N-(lissamine Rhodamine B sulfonyl)dipalmitoylphosphatidylcholine is the same in the two lipid leaflets of phosphatidylcholine bilayers containing the probe. In the liquid-crystalline state, the probe molecules aggregate above a threshold amount, approximately 0.2 mol/mol phospholipids. Above this threshold value, the surface density of the free probe molecules is constant, and all probe molecules added are incorporated in the aggregated form. The aggregation of the probe increases by approximately 20% when the medium pH is lowered to 4. In the gel state, the probe aggregation is higher than that in the liquid-crystalline state, and the free probe molecules distribute unevenly in the bilayer surface. Even though the results obtained in our model system cannot be directly extrapolated to all model systems, we point out that care is to be taken in the use of the probe. In fact, only in membranes in the liquid-crystalline state in which the amount of probe molecules to phospholipid molecules is lower than 1:7 the fluorescence response of the probe is independent of the pH changes and of the molecular aggregation.
在含有荧光探针N-（丽丝胺罗丹明B磺酰基）二棕榈酰磷脂酰胆碱的磷脂酰胆碱双层膜的两个脂质小叶中，该荧光探针的表面密度是相同的。在液晶态下，探针分子在超过阈值量（约0.2摩尔/摩尔磷脂）时会聚集。高于此阈值时，游离探针分子的表面密度是恒定的，并且所有添加的探针分子都以聚集形式掺入。当介质pH降至4时，探针的聚集增加约20%。在凝胶态下，探针的聚集高于液晶态，并且游离探针分子在双层表面分布不均匀。尽管在我们的模型系统中获得的结果不能直接外推到所有模型系统，但我们指出在使用该探针时要小心。事实上，只有在液晶态的膜中，当探针分子与磷脂分子的比例低于1:7时，探针的荧光响应才与pH变化和分子聚集无关。
